1. Field of the Invention
The present invention relates generally to printing machines including a plate adapted to rotate about its axis and carrying at its periphery a plurality of object supports having a top face adapted to receive an object to be printed and a plurality of workstations distributed circumferentially around said plate in line with the trajectory of said object supports and some of which are printing stations and others of which are treatment stations.
2. Summary of the Invention
The invention provides a printing machine including a plate adapted to rotate about its axis and carrying at its periphery a plurality of object supports having a top face adapted to receive an object to be printed and a plurality of workstations distributed circumferentially around the plate in line with the trajectory of the object supports and some of which are printing stations and others of which are treatment stations, wherein at least one of the object supports includes lifting means adapted to raise the object relative to the top face of the object support.
This has the advantage that it facilitates some object treatment operations (see below).
The lifting means are advantageously connected to a suction head adapted to preserve the projecting position of the object corresponding to that it initially occupied on the object support.
The lifting means advantageously include at least one tube mounted to slide through holes through the object support and the plate.
The tube is preferably fastened at the bottom to a spacer fastened to a shoe adapted to cooperate slidingly with a guide rail fixed under the object support and passing through an opening in the plate.
To raise the object, the spacer is adapted to cooperate with fixed cam means carried by a frame of the machine having a lifting ramp and a raised position maintaining bearing surface.
Alternatively, the spacer is adapted to cooperate with the shoe of a lifting actuator and with a raised position maintaining bearing surface formed on the top of fixed cam means carried by a frame of the machine; as a safety feature the shoe includes a lifting ramp in case the actuator should break down.
The spacer advantageously cooperates with the cam means and/or the shoe via a roller.
The lifting means preferably include cam means and a lifting actuator and the width of the lifting ramp of the cam means is less than that of its position maintaining bearing surface whereby a cut-out is defined in which the shoe of the actuator slides.
A beneficial application of the above object supports is to the situation in which at least one of the treatment stations is a heat treatment station, in particular a high-temperature heat treatment station. In accordance with the invention, the object is raised at this treatment station in the direction of the heat source and the flow of heat, for drying the ink on the printed object, for example, has little effect on the object support itself or the plate, the object being treated being at a distance from them so they are not deformed by the heat, which would reduce the print quality.
In this type of application the end of the tube advantageously has an endpiece made from a material that is resistant to high temperatures, to prevent thermal conduction phenomena.
For improved thermal protection of the object support and the plate, the heat treatment station can be a high-temperature station at which there are two radially spaced screens defining a slot through which the tube passes in the raised position, the screens being halfway up the emergent travel of the tube.
A slot cover is advantageously adapted to cover the slot during phases in which there are no objects to be treated.
Another beneficial application of the above object supports is to the situation in which the objects must be turned over, for example to print both sides; in this case at least one workstation is an overturning station.
The overturning station advantageously includes a pallet associated with actuator means adapted to move the pallet vertically and radially and to turn it about an axis; the pallet has holding suction nozzles at the end.
The actuator means are adapted to insert the pallet radially into the space between the object support and the object when the object is raised by the lifting means.
The object supports are preferably adjustably mounted on the plate.
In a preferred embodiment of the invention the object support bears on a hollow rod which is externally screwthreaded and screwed into a screwthread of the plate and a screw screwed into the object support passes through the hollow rod.
The screwthread of the plate is advantageously an internal screwthread of a hollow screw surrounding the rod and screwed into the plate by means of a screwthread on its outside face.
In a preferred embodiment of the invention the lifting means comprise two sliding tubes.
The present invention also provides an object support for a printing machine having an object-receiving top face which includes lifting means for raising the object relative to its top face.
The lifting means advantageously have the features of the object support of the above printing machine.
To explain the invention more clearly, one embodiment of the invention, shown in the accompanying drawings, will now be described by way of purely illustrative and non-limiting example.